Simple model of local ordering of DPPC lipids in contact with cholesterol

Abstract

Smaller area per molecule in a DPPC-cholesterol multicomponent monolayers than in pure DPPC suggests that DPPC lipids straighten when in contact with cholesterol. Using flexible strings model that imitates entropic repulsion between lipid chains in the membrane, one can reproduce the DPPC-cholesterol area per molecule diagram at a low cholesterol concentration. Using an analytical interpolation we construct a pure cholesterol membrane, which allows us to calculate area per molecule in cholesterol “membrane” with small DPPC concentration. The last result suggests the area per lipid in a large cholesterol concentration DPPC membrane. The parameters found by fitting our model results to the experimental area-concentration diagram imply that cholesterol exerts greater lateral pressure in the membrane than DPPC.